1. Field of the Invention
The present invention relates to a magnetic bubble recording device, and more particularly to a magnetic bubble recording device in which writing, reading and erasure are carried out optically with respect to magnetic bubbles.
2. Description of the Prior Art
Development of magnetic bubble recording devices has proceeded in conjunction with that of semiconductor recording devices. Since magnetic bubble recording devices are characterized in having nonvolatile memories and in that they can operate in a stable manner at high temperatures, their use as memories has been increasing.
An example of the configuration of a conventional magnetic bubble recording device is shown in FIGS. 1A and 1B. FIG. 1A is a cross-sectional view thereof, while FIG. 1B is a top plan view thereof.
The conventional magnetic bubble recording device shown in FIGS. 1A and 1B comprises the following components: a garnet substrate 1 where magnetic bubbles are formed; a soft magnetic layer 2 adapted to transfer magnetic bubbles and formed of permalloy or the like; an insulating spacer layer 3; and a conductive film (wiring pattern or the like) 4 for generating a bubble transferring magnetic field or for receiving or transmitting various types of signals at the time of the recording and reproduction of information.
To transfer a magnetic bubble in a conventional magnetic bubble recording device, the soft magnetic layer 2 is magnetized in the direction of a rotating magnetic field, the latter rotating in the direction of a given plane (parallel with the surface of the substrate 1) and being produced by supplying an electric current to, for instance, a coil placed outside the magnetic bubble recording device or the conductive film 4 shown in FIG. 1B. The magnetic bubble held on the garnet substrate 1 in FIG. 1A is attracted and transferred to a bubble trapping point (a point where magnetization occurs) which is produced and displaced along the peripheral edge of a pattern of the soft magnetic layer 2.
In addition, the formation of a magnetic bubble is carried out by, for instance, allowing an electric current to flow to the conductive film 4 located adjacent to a specific point of the pattern of the soft magnetic layer 2 and by applying a local vertical magnetic field produced thereby to the garnet substrate 1. In addition, the detection of the presence or absence of the magnetic bubble is carried out by a detector (magnetic sensor) such as a Hall element disposed midway in the pattern of the soft magnetic layer 2.
With such a conventional magnetic bubble recording device, however, it is necessary to effect fine processing when providing a wiring pattern of signal lines for writing and reading on the chip as well as installing a magnet, a coil, etc., for producing the bias magnetic field. As a result, it has been difficult to provide a compact, lightweight recording device at low cost.
To overcome the above-described problems, the assignee of the invention has earlier proposed a method of optical writing using a magnetic bubble and a method of optical reading using the same in U.S. patent application Ser. Nos. 801,401 and 883,921. If these methods are used, the patterning provided for writing on the chip or reading therefrom does not need to be complicated.